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Summary
| Description |
Impact pseudotachylite (cut surface; field of view 16.6 cm across) - impact-fractured granite (orangish areas - K-feldspar & quartz) with grayish- to blackish-colored impact pseudotachylite (impact melt) vein fillings. The rock name "pseudotachylite" has long been applied to vein-filling impact melts in impact-fractured rocks - the impact melt has a glassy to cryptocrystalline texture. Fault zone movement can also generate melt, which cools down to very similar-looking material. Fault zone melt rocks have also been called pseudotachylites. The term “pseudotachylite” was originally defined based on melt rocks of impact origin. Despite this, Reimold & Gibson in 2005 published a 53-page paper that basically says “you shouldn't call impact melts pseudotachylites anymore” and “only fault zone melt rocks should be called pseudotachylites”. A simpler, more logical solution is two have two terms: "impact pseudotachylite" & "fault zone pseudotachylite". The sample shown here is impact-fractured basement rock from well below the original crater floor of the Rochechouart Impact Crater in west-central France. The impact event, basement rock fracturing event, and pseudotachylite formation event all occurred 214 million years ago, during the Norian Stage of the mid-Late Triassic. ------------------ Reference on pseudotachylite: Reimold, W.U. & R.L. Gibson. 2005. “Pseudotachylites” in large impact structures. in Impact tectonics. Impact Studies 8: 1-53. |
| Date | |
| Source | Impact pseudotachylite (Rochechouart Impact Crater, 214 Ma, Late Triassic; west-central France) |
| Author | James St. John |
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This image was originally posted to Flickr by jsj1771 at https://www.flickr.com/photos/47445767@N05/14804604355. It was reviewed on 10 August 2014 by FlickreviewR and was confirmed to be licensed under the terms of the cc-by-2.0. |
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| Date/Time | Thumbnail | Dimensions | User | Comment | |
|---|---|---|---|---|---|
| current | 05:29, 10 August 2014 | | 1,820 × 794 (1.35 MB) | Tillman | Transferred from Flickr via Flickr2commons |
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